<!DOCTYPE html>
<meta charset="utf-8">
<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1928724">

<style>
*:only-child {
  contain: size layout paint;
}
</style>

<script>
document.addEventListener("DOMContentLoaded", () => {
  a.getBoundingClientRect();
  a.appendChild(c);
  b.scrollBy();
})
</script>

<body>
<svg>
<animateMotion id="b">
</animateMotion>
<foreignObject id="a">
<article>
<data id="c">
